fix strings to new convention

Author: gboehl

econpizza/solvers/steady_state.py

@@ -31,8 +31,7 @@ def _get_stst_dist_objs(self, res, maxit_backwards, maxit_forwards):
     elif jnp.isnan(distSS).any():
         mess += f"Forward iteration returns NaNs. "
     elif distSS.min() < 0:
-        mess += f"Distribution contains negative values " + \
-            f"({distSS.min():0.1e}). "
+        mess += f"Distribution contains negative values ({distSS.min():0.1e}). "
     if cnt_backwards == maxit_backwards:
         mess += f'Maximum of {maxit_backwards} backwards calls reached. '
     if cnt_forwards == maxit_forwards:
@@ -170,8 +169,7 @@ def solve_stst(self, tol=1e-8, maxit=15, tol_backwards=None, maxit_backwards=200
                 err) else f" (max. error is {err:1.2e} in eqn. {errarg})"
             mess = f"Steady state FAILED{location}. {res['message']} {mess}"
         else:
-            mess = f"{res['message']} WARNING: Steady state error is {
-                err:1.2e} in eqn. {errarg}. {mess}"
+            mess = f"{res['message']} WARNING: Steady state error is {err:1.2e} in eqn. {errarg}. {mess}"
         if raise_errors:
             raise Exception(mess)
     elif verbose: